The Republican challenger cast his vote near his Massachusetts home early this morning before heading off on election day rallies in Ohio and Pennsylvania, traditionally a Democrat stronghold. Mr Obama voted last month, a move intended to encourage Americans to vote early.

The American public are currently voting in what analysts are predicting could be the closest race yet to the White House, with the two candidates neck-and-neck heading into today.

Mr Obama held a slender lead in crucial swing states, as more than 100million Americans began to cast their vote. More than 30million early votes have already been lodged.

With that in mind, attention is turning to the battlegrounds in the race for the presidency – traditionally marginal states such as Ohio, Wisconsin and Iowa in the Midwest and Florida, Virginia and North Carolina on the eastern seaboard.

Late last night, both men made last-ditch pleas for votes with impassioned speeches promising to make a real difference to the lives of everyday Americans.

Barack Obama spent the day in Chicago (Picture: Reuters)

In his closing remarks at a last-minute rally in Ohio, Mr Romney promised the American public ‘real change’ if he was elected.

‘The election comes to this, do you want four more years like the last four years? Or do you want real change?’ he said.

‘Now president Obama promised change but couldn’t deliver it. Now I not only promise change but I have a record of achieving.

‘If you are tired of being tired then I ask you to vote for real change and to make that happen tomorrow.’

He added: ‘With the right leadership, America is going to come roaring back.

‘The only thing that stands between us and some of the best years that we could ever imagine is lack of leadership and that is why we have elections.

‘Tomorrow is a moment to look into the future and imagine what we can do.’

Meanwhile on his final day of campaigning in Iowa, Obama urged the thousands of people in front of him not to ‘give up on change’.

‘We’ve come too far to turn back now,’ the president said earlier in Ohio.